Rotary hydraulic device with nutating gear

ABSTRACT

In a reduction gear for a hydraulic motor there is a stationary gear ring in the motor housing. For engagement with this stationary gear ring is a nutating disc having a gear ring on its one side and in its center being coupled to an output shaft. On its other side the nutating disc is engaged by pistons under influence of a hydraulic liquid, which give the nutating disc a wobbling and rotating movement. The last mentioned part of this movement is both transferred to a distributing disc controlling the supply of hydraulic liquid to the pistons and also being transferred to the output shaft, which is driven at a reduced speed in relation to the distributing disc.

United States Patent 1191 v Berg j A 1111 3,823,649 1451 July 16,1974

ROTARY HYDRAULIC DEVICE WITH NUTATING GEAR FoREioN PATENTS OR APPLlCATlONS 249,152 7/1926 ltaly 91/503 Primary Examiner-William L. Freeh Attorney, Agent, or Firm-Young and Thompson In a reduction gear for a hydraulic motor there is a ABSTRACT stationary gear ring in the motor housing. For engagement with this stationary gear ring is a nutating disc having a gear ring on its one side and in its center being coupled to an output shaft. On its other side the nutating disc is engaged by pistons under influence of a hydraulic liquid, which give the nutating disc 8. wobbling and rotating movement. The last mentioned part of this movement is both transferred to a distributing disc controlling the supply of hydraulic liquid to the .pistons, and also being transferred to the output shaft,

which is driven at a reduced speed'in relation to the distributing disc.

5 Claims, 4 Drawing Figures PATENTEDJUL 1 6 914 3'. 823.649

' sum 2 0F 3 INCLINATION ANGLE OF NUTATING DISC (I DEGREES 1 40- GEAR RATIO m 1 cos 6c I l I I SPEED REDUCTION, NUMBER OF TIMES Fig.2

PATENTEDJUU 51974 SHEET 3 OF 3 on om 9 SEES F P P h on ow 0 o fan}; w E cm on ow v d4 q A A Ow? 1 omP 7 G E m EYES. ow dw 0w 9 ROTARY HYDRAULIC DEVICE WITH NUTATING GEAR The present invention relates to a reduction gear for a hydraulic motor.

It is an object of the present invention to provide a reduction gear of a very simple kind and well suitable for machines in which mechanical energy is converted into hydraulic energy and vice versa, e.g. hydraulic pumps and hydraulic motors.

Motors of that type in general work according to the following'two main principles:

a. A number of pistons, mounted in the motor housing, press against an inclined disc fastened to the motor shaft and transform'the linear movement of the pistons into a rotating movement.

b. A number of pistons, mounted in the motor shaft, press against an inclined disc fastened to the motor housing and cause the motor shaft to rotate.

Characterizing for both these motor types isan exceptional high working pressure, high rotational speed and relatively low torque. The high working pressure causes sealing problems difficult to master and great friction losses, which both cause a high efficiency only within a little range. Assufficient effect can be calculated according to the formula H =P'Q/450, in which P is the pressure in kp/cm and Q is the flow in l/min,

it is evident that low values of P and Q are advantais wanted it is of course possible to decrease the supplied oil quantity through the choice of a suitable pump, but in such cases where the motor shall be included in a hydraulic system already definite,'e.g. in the mobile hydraulics, where the pumpcapacity isdefined through other functions, this possibility does not exist. The only solution is to apply to the motor some sort of a gear box.

This invention has prepared the way for other, considerably better and simplier solutions.

Reference should be had to the accompanying drawings forming a part of this specification, in which FIG. 1 is a hydraulic'motor, shown partly in section and provided with areduction gear according to the invention, t

FIG. 2 is agear ratio diagram,

FIG. 3 is an effect diagram, and

FIG. 4 is a sketch used as basis for some formulas.

In FIG. 1 the reference numeral 1 designates a motor housing, in which is mounted an output shaft 2. In its inner end the shaft 2 is through splines 3 in engagement with the center of a nutating disc 4, this being in its outer collar shaped part provided with a gear ring 5. The upper part of the disc 4 is provided with a ball shaped pin 6 which is located in a corresponding hole in the underside of an outer part of a distributing disc 7, mounted for rotation in the motor housing 1.

In engagement with the side of the nutating disc 4, I

which is opposite to that having the gear ring 5, are pistons 9, in the present example of the description being six in number (one is shown in FIG. 1). Through grooves 8 made in the distributing disc 7 three of the pistons 8 are in connection with the inlet 10 for the hydraulic liquid, whereas the three other pistons 8 are in connection with the outlet 11 for the same liquid.

When supplying hydraulic liquid to the pistons 8 these will give the nutating disc 4 a rotating and wobbling movement, by which consecutive parts of its gear ring 5 will be brought into engagement with a gear ring 12 integral with the motor housing 1. In the center of the nutating disc 4 the rotating movement is transferred to the output shaft 2. The rotational speed of the shaft 2 is dependent on both the piston speed, which is defined by the oil quantity supplied, and the gear ratio of rings 5 and 12. The rotational speed of the pin 6 is not effected by the inclination angle. Its ratio is always 1: 1.

In the effect diagram according to FIG. 3 is shown an example of a motor, the six pistons of which have a diameter of IS mm, which at 150 r.p.m. transfer 30 kpm at a flow of l/min and an oil pressure of 40 kp/cm. The inclination angle a=l7,5. If friction, leakage and flow losses are disregarded the torque M is calculated according to the formula and the rotational speed na of the output shaft 2 according to the formula Further the rotational speed ns of the distributing'disc 7 is calculated according to the following and the piston speed K is calculated according to the following K tga'ns'r"ir/30OO. For the formulas above see also FIG. 4 P=oil pressure, kp/cm Q=oil flow, l/min M,,=torque, kpm na=r.p.m., output shaft ns=r.p.m., distributing disc I a==the inclination angle of the nutating disc, degrees r=pitch radiusof the pistons, cm

a=number of pistons, totally y=piston area, each, cm

k=piston speed, m/sek Motors within the scope of the present invention and having different data can be made in many different ways, e.g. through selecting the number of pistons, the piston area, the gear ratio by and so on.

The motor described above is reversible.

Through providing the distributing disc 7 with an input, driven shaft 13 the device can be used as a pump. The nutating disc 4 driven by the shaft 13 and the distributing disc 7 thereby force the six pistons 8 to bring about a reciprocating movement in their cylinders.

The pitch diameter of the gear ring 5 is always larger than the pitch diameter of the stationary gear ring 12. If on disc 4, number of teeth of the gear ring 5=22 and number of teeth of the stationary gear ring l2=2l, pitch diameter of the gear ring 5=88 and pitch diameter of the stationary gear ring l2=84, the gear ratio will be 22. i

What I claim is:

l. A rotary hydraulic device comprising a housing, a stationary gear ring in said housing, a rotatablenutating member in said housing, said member having a gear ring thereon in partial engagement with said stationary gear ring, an annular series of reciprocable pistons in said housing, said nutating member being in engagement with said pistons, means to supply hydraulic fluid to said pistons, said nutating member having a pin thereon concentric with said nutating gear ring, a shaft rotatable in said housing, and means connecting said pin for universal pivotal movement with said shaft at a point on said shaft spaced from the axis of rotation of said shaft.

2. A device as claimed in claim 1, and a second shaft coaxial with the first-mentioned shaft and rotatable in said housing, and means articulatedly interconnecting said nutating member and said second shaft for conjoint rotation while permitting nutating movement of number of teeth on said stationary gear ring. 

1. A rotary hydraulic device comprising a housing, a stationary gear ring in said housing, a rotatable nutating member in said housing, said member having a gear ring thereon in partial engagement with said stationary gear ring, an annular series of reciprocable pistons in said housing, said nutating member being in engagement with said pistons, means to supply hydraulic fluid to said pistons, said nutating member having a pin thereon concentric with said nutating gear ring, a shaft rotatable in said housing, and means connecting said pin for universal pivotal movement with said shaft at a point on said shaft spaced frOm the axis of rotation of said shaft.
 2. A device as claimed in claim 1, and a second shaft coaxial with the first-mentioned shaft and rotatable in said housing, and means articulatedly interconnecting said nutating member and said second shaft for conjoint rotation while permitting nutating movement of said member relative to said second shaft.
 3. A device as claimed in claim 1, and valve means for said hydraulic fluid supply means carried by said shaft.
 4. A device as claimed in claim 1, the number of teeth on said nutating member being different from the number of teeth on said stationary gear ring.
 5. A device as claimed in claim 4, the number of teeth on said nutating member being greater than the number of teeth on said stationary gear ring. 